Reaction chamber



1944- D. L. CAMPBELL ET AL 2,340,930

REACTION CHAMBER Filed Jan. 20. 1940 2 Sheets-Sheet l -Q Q E Q k a Q k 8'3- 3 n *4 Q Pi Q a 5 V) N MN *Q 14 EM I Feb. 8, 1944.

D. L. CAMPBELL ET AL 2,340,930

REACTION CHAMBER Filed Jan. 20,' 1940 2 Sheets Sheet 2 Patented Feb. 8,1944 REACTION CHAMBER Donald L. Campbell, Roselle Park, and George B.Cook, Summit, N. J., assignors to Standard Oil Development Company, acorporation of Delaware Application January 20, 1940, Serial No. 314,766

2 Claims. (01.196-133) The present invention relates to the conversionof mineral oils into relatively higher and into relatively lower boilingconstituents. The invention is particularly directed to an improvedreaction chamber in which petroleum hydrocarbons may be held for thedesired time period under temperature and pressure conditions adapted tosecure cracking. The reaction chamber of the present invention comprisesan outer'vessel and a concentrically disposed inner vessel comprising airangible section whereby the direction of flow of the fluid in saidreaction chamber is reversed between said vessels.

It is well known in the art to convert petroleum oils into moredesirable products by subjecting feed oils to elevated temperatures andpressures for various time periods, which periods are usually measuredin terms of yield per unit throughput, generally termed conversion perpass. The

various variable operation factors are adjusted to secure the desiredyield and depend, in general, upon the particular feed material beingtreated and upon the yield and quality of products desired. In theseoperations it is essential that the feed oil be maintained at desiredtemperature and pressure conditions for a suiiicient length of time.Thus, the common practice is to utilize a reaction chamber or so-calledsoaking drum designed to hold the oil being treated at the desiredtemperature and pressure for the optimum time period. However, manyreactions result in the formation of a hard carbonaceous coke productand it is necessary that this formation be removed periodically from thereaction chamber or soaking drum. Furthermore, in order to secure betterresults with respect to the overall cracking operation, it is desirablethat the flow of oil be reversed, preferably be passed first downwardlyand then upwardly in the reaction chamber. For example, at temperaturesin the range from 850 F. to 950 F. and pressures in the range from 100pounds to 750 pounds per square inch gauge, which are the optimumconditions for carrying out in a reaction chamber the thermal crackingof reduced crude with or without cycle as oil, the material present atany point in the reactor exists in two phases, the liquid and the vaporphase. It has been found by experience that in order to obtain thehighest possible octane number on the gasoline made in the thermalcracking operation and to obtain the greatest possible yield of thisgasoline, it is desirable to crack under the most severe conditions thatare practicable. The limitation with regard to the reaction yesselcondition is the formation of deleterious coke in this vessel. It hasfurther been found by experiment that within the practical limitsmentioned, it is best to crack the components in the vapor phase for ashort time at high temperature, and the components in the liquid phasefor a relatively longer time period at a lower temperature. This is mostreadily accomplished by causing the mixture to flow downwardly throughone reaction zone and then upwardly through a second reaction zonewithin the reaction chamber. The liquid phase drops very rapidly throughthe first zone and rises much more slowly through the second zone. Thevapors flow rapidly through the first zone and bubble even more rapidlyupwardly through the second zone. Since the reaction absorbs heat, thetemperature is lower in the second zone than in the first zone. Thus,the vapors are cracked in the first zone for a relatively short time ata relatively high temperature and pass through the second zone withoutmuch further cracking, while the liquid is cracked principally in thesecond zone for a relatively long time period.

Therefore, suggestions have been made that the reaction chamber comprisean outer vessel having concentrically disposed therein an inner vesselso arranged that the flow of oil through the reaction chamber isreversed between the respective vessels.

Heretofore this type of reaction chamber could not be economicallyemployed commercially due to the fact that a carbonaceous product formedbetween the outer and inner vessel at the bottom of the reaction zone,making cleaning of the reaction chamber extremely diflicult. Ourreaction chamber comprising an outer metallic vessel and aconcentrically disposed inner frangible vessel completely solves thisdifficulty and renders the use of this type of equipment entirelyfeasible.

When employing our invention the frangible section may be broken and thecarbonaceous product readily removed in an efficient and economicalmanner.

Our invention may be readily understood by reference to the attacheddrawings illustrating one modification of the same. Figure 1 shows adiagrammatical flow plan of a normal cracking operation. Figure 2 is asketch illustrating in detail a suitable construction of a reactionchamher in accordance with the present invention. Referring specificallyto the drawings, Figure l is a diagrammatical flow plan of a typicalcracking operation. For purposes of description it is assumed that thefresh feed is a fraction boiling in the range above about 700 F. In thisoperation the fresh feed is introduced by means of feed line I into thebottom of primary bubble tower 2 which is provided with suitablefractionating and cooling means. The feed, together with cycle oil, iswithdrawn from the bottom of primary bubble tower 2 and introduced intofurnace 4 by means of line 3. Furnace 4 is designed so as to secureoptimum heat transfer as the feed stock flows through tubes in theradiant and convection sections and to raise the temperature of the oilto cracking temperatures. The total feed is passed from furnace 4 bymeans of line 5 into soaking drum or reaction chamber 6 which permitsadditional time under cracking conditions. Reaction chamber or soakingdrum 6 comprises an outer vessel having concentrically disposed thereina frangible vessel 56. The feed oil under cracking conditions isintroduced into the top of the soaking drum. The oil flows downwardly inthe area between vessel 6 and vessel 50 and upwardly within vessel 50.The oil is withdrawn from reaction chamber 6 by means of line I andpassed through pressure reducing valve 8. The cracked products pass intoevaporator 9 from the bottom of which tar or fuel oil of the desiredgravity is removed by means of line 5l, cooled in cooler 52, andwithdrawn from the system. The vapors pass overhead from evaporator 9through line I!) into primary bubble tower 2. Cycle stock accumulates inthe bottom of primary bubble tower 2 and vapors pass overhead by meansof line I l and are introduced into secondary bubble tower [2 which isprovided with suitable fractionating and cooling means. The temperatureat the top of tower I2 is controlled so as to produce an overheaddistillate of the desired end point which is removed by means of line l3and condensed in cooler M. The gas is separated from the distillate indistillate drum I 5 and removed by means of line I! while the distillateis removed by means of line l6. Heating oil may be withdrawn from thebottom of tower l2 by means of line 18.

Figure 2 illustrates in detail reaction chamber 6. Reaction chamber 6comprises an outer shell 20 and an inner concentrically disposed section2|. Feed material is introduced by means of line 5. The feed oil flowsdownwardly in the zone between the outer shell and the concentricallydisposed vessel and then upwardly within said concentrically disposedvessel. The oil is then withdrawn by means of line I. In a preferredmodification of the invention, the inner concentrically disposed vesselcomprises at least one lower section frangible in nature. This lowersection '22 is of sufiicient length so that under the conditions ofoperation the coke level will never build up above said frangiblesection. This section may be attached to a permanent section 23 by anysuitable means, as for example, by means of a flange or by threads or bymeans of wires, rods or removable beads positioned beneath the openedend of the inner vessel. Although substantially the entire area of theinner vessel may comprise frangible material, a preferred modificationis an inner vessel, the upper twothirds of which comprises non-frangiblematerials, as for example, steel, and the lower third of which comprisesfrangible material. The frangible material may comprise any suitablecomposition having heat resisting properties. A

preferred composition comprises 30% asbestos fiber and 70% Portlandcement. However, other compositions of asbestos fiber and heat resistingbinders are satisfactory, as well as tile and concrete using temperatureresisting cements and sand or gravel or petroleum coke or coke frombituminous coal as the aggregate.

The process of the present invention is not to be limited by any theoryor mode of operation, but only in and by the following claims in whichit is desired to claim all novelty in so far as the prior art permits.

We claim:

1. Apparatus for causing rapid downfiow of heated oil and its vaporsfollowed by slower upward flow of the oil and more rapid upward flow ofthe gases comprising an outer metal cylindrical drum havingconcentrically disposed therein an inner cylindrical vessel having anupper edge connected to an upper part of the inner surface of said outerdrum and lower end not attached to the bottom of said drum, said innercylindrical vessel having at least the lower part thereof formed of atemperature-resisting material selected from the class consisting ofasbestos fibre mixed with binders, tile and concrete, major part ofinner surface of said drum and entire outer surface of said inner vesselmaking an annular chamber of relatively large capacity, said drum havingan inlet connected to a mineral oil supply for introducing feed into thetop of said annular chamber, said drum having an outlet for withdrawingoil and vapors from top 0f "said inner cylindrical vessel whereby thusthe feed flows downwardly through said annular chamber then around thelower edge of said inner cylindrical vessel and upwardly through saidinner cylindrical vessel, and said drum also having -a third opening ofsmaller cross section than that of the drum for removing 'coke 'asrequired.

2. Apparatus for causing rapid downfiow of heated oil and its vaporsfollowed by slower upward flow of the 'oil and more rapid upward flow ofthe vapors comprising an outer metallic cylindric'al drum havingconcentrically disposed therein an inner cylindrical vessel having theupper edge connected to an upper'part of the inner surface of said outerdrum and lower end not connected to the bottom of said drum, said innercylindrical vessel having a frangible part extending from the bottom ofsaid inner cylindri cal vessel about one-third the length thereof andthe remainder of said inner cylindrical vessel being composed of anunfrangible metallic material, major part of inner surface of said drumand entire outer surface of said inner vessel making an annular chamberof relatively'large capacity, said drum having an inlet connected 'to amineral oil supply for introducing feed into the top of said annularchamber, said drum having an outlet for withdrawing .oil and vaporsfrom'top of said inner "cylindrical vessel whereby thus the feed flowsdownwardly through said annular chamber then around the lower edge ofsaid inner cylindrical vessel and upwardly through said innercylindrical vessel, and said drum also having a third opening of smallercross section than that of the drum 'for removing 'c'oke as required.

DONALD L. CAMPBELL. GEORGE 'B'. 'COOK.

